In accordance with the normal growth of a man, the first set of teeth are replaced with the second, the man cuts and chews food, speaks precisely, and has good dental appearance with the second teeth. However, when one or more second teeth are damaged due to a variety of dental diseases, such as decayed teeth or gingival diseases, it is very difficult for a patient to eat or speak precisely. Such damaged teeth also cause bad dental appearance, which sometimes impedes the personal relationships of the patient.
It is thus necessary to treat or replace such damaged teeth with dentures in an effort to allow the patients to easily eat, speak precisely and to restore good dental appearance thereby allowing the patients to restore self-confidence in their personal relationships. In recent years, dental treatment has been performed to maintain dental health and allow patients to overcome an unsettled feeling caused by damaged teeth. It is necessary for the dentures to precisely meet the different dental conditions of patients. The objective of the dentures is to partially or fully restore the natural function and beauty of the teeth.
As is known to those skilled in dentistry and prosthodontia, dentures are the dental prostheses used for replacing one or several of the teeth when the teeth and the surrounding tissues are damaged or missing. Such dentures are called “artificial teeth” or “false teeth”. In a general sense, the dentures mean consist of dental prostheses with pontics, and involve partial dentures, full dentures and dental bridges. In a detailed description, the dentures include dental caps, crowns, bridges, veneers, inlays, onlays, peripheral caps and crowns, and inlay bridges retained on abutment teeth when replacing one or more missing teeth with pontics arranged on the remaining roots of the missing teeth.
As described above, the dentures are typically classified into three types: bridges, partial dentures and full dentures. The bridges are used for replacing one or more missing teeth with pontics, are retained by crowns which are fitted to the abutment teeth around where a teeth is missing and are connected to the pontic crowns. The conventional bridges are classified into fixed and removable types. The fixed bridges are semi-permanently retained in the dental cavities, and variously classified in accordance with their sizes, production and uses.
Different from such bridges, the partial dentures are artificial teeth, which are retained by natural teeth and the surrounding tissues to restore the function of the damaged teeth when one or more teeth and the surrounding tissues are damaged. The partial dentures take the place of the damaged teeth and restore a good dental appearance.
Full dentures are artificial teeth, which are made using a variety of materials and fitted to patients having no natural teeth. The full dentures are thus called “final treatment and final dentures for dental patients. Using such a full denture, a patient can cut and chew food, speak precisely, and have a good and natural dental appearance. The full dentures are designed, made and fit to patients without adversely-affecting the patient's soft tissues.
The present invention relates to such a fixed bridge, which is used for replacing one or more missing teeth with pontics retained by crowns fitted to the abutment teeth around the missing teeth. The fixed bridge restores the food cutting and chewing function of the teeth, and corrects bad pronunciation, as well as providing a natural dental beauty. Some conventional examples of such bridges are briefly described below.
An example of such conventional bridges is a crown bridge. The crown bridge consists of a pontic crown integrated with two caps, which have the same shape as that of natural teeth. The caps of the crown bridge are fitted over the abutment teeth around the missing tooth, thus restoring the function of natural teeth.
As shown in FIG. 6, in order to fit such a crown bridge to a patient, two natural teeth 200 around a missing tooth are each cut by 2˜3 mm at their top surfaces and 1˜3 mm at their side surfaces, resulting in the two abutment teeth 200 being cut by about ⅓ of their original sizes. An impression is then taken of the teeth and the surrounding tissues. After taking the impression, a crown bridge is made of dental ceramic or dental acrylic resin through a casting process on the basis of the impression. The crown bridge has a pontic with two crown-type caps, and the two caps are fitted over the abutment teeth 200 such that the pontic replaces the missing tooth. In such a case, the dental ceramic or dental acrylic resin provides shape and color almost equal to that of the natural teeth.
Such a conventional crown bridge is advantageous in that it is easily made and fitted to a patient, and has a low treatment cost. However, this crown bridge is problematic in that it requires the cutting of natural teeth around a missing tooth to provide abutment teeth, over which the crown-type caps of the bridge are fitted. Dental treatment using such a crown bridge is thus very difficult and may damage dental nerves, resulting in pain to patients while the abutment teeth are cut. In addition, due to the cutting, the abutment teeth may not be effectively used for a normal period of time. The crown bridge easily allows impurities, such as food, to be get stuck between the teeth around the bridge. These impurities are very difficult to remove. Another problem of such a crown bridge resides in that its occlusal surfaces may be holed and/or a gap may be formed between the crown-type caps. In such a case, the abutment teeth and another tooth around the crown bridge are decayed. The crown bridge thus may severely damage the natural teeth.
In an effort to overcome such problems experienced in the conventional crown bridge, there exists the artificial replacement of missing teeth using implants. The implants are dental screws, which are driven into the alveolar bone of the maxilla or mandible of a patient and provide a platform for retaining an artificial tooth in the space of a missing tooth. A representative dental implant has a root shape, and is driven into a predetermined position of the alveolar bone.
When an implant is driven into the alveolar bone, a disposable mount is used as a means of connecting an implant driving tool. In the case of a screw-type implant, the disposable mount is a removable extension of the implant. Such a removable extension has a hexagonal nut-shaped head, which engages with a socket used for driving the implant into a predetermined position of the alveolar bone. After completely driving the implant into the alveolar bone, the disposable mount is removed and discarded. A cover bolt is attached to the top of the implant. After the implant with the cover bolt is driven into the alveolar bone, the tissue of the alveolar bone surrounding the implant grows around the implant for several months, and so the implant is fixed to the tissue.
When the surrounding tissue of the alveolar bone is securely holding the implant, the cover bolt is removed from the implant prior to attaching an impression copying to the implant. An impression of the implant, the teeth around the space and the surrounding tissues is taken, and a denture is made on the basis of this impression. The denture is retained by the abutment teeth using a retaining means. In such a case, the abutment teeth act as a platform fixing the denture to the implant.
However, the artificial replacement of a missing tooth using such an implant is problematic in that it requires three months minimum to about one year maximum to complete the dental treatment, and increases the dental treatment cost. In addition, it is necessary to drive the implant into the alveolar bone while averting the dental nerves and blood veins, and so the implant must be performed by a highly skilled dentist. The artificial tooth fixed by such an implant is inferior in its resistance to lateral impact. The implant may cause severe damage to the maxilla or mandible of a patient when the artificial tooth is laterally impacted. PCT/US1997/12673 (Korean Patent Application No. 1999-7000350) discloses a dental technique designed to overcome such problems experienced in the conventional implant.
On the other hand, Korean Patent Application No. 2000-67885 discloses a dental prosthesis designed to overcome the problems experienced in the conventional crown bridges. As shown in FIG. 7 of the accompanying drawings of this invention, the dental prosthesis consists of an artificial tooth 20, which is provided with a slit 21 extending to ⅔ the total height of the tooth 20. The dental prosthesis also has an inlay 22, which consists of a retaining part 25 and an insert part 27. The retaining part 25 has a plurality of projections 24, and is fixed to an abutment tooth by the projections 24. The projections 24 are downwardly inclined at a predetermined angle. The insert part 27 is inserted into the slit 21 of the artificial tooth 20.
The above dental prosthesis disclosed in Korean Patent Application No. 2000-67885 is advantageous in that it overcomes the problems experienced in the conventional crown bridges and conventional implants. That is the dental prosthesis does not damage the teeth around a missing tooth, and reduces the operational time and cost during a dental treatment, in addition to simplifying the dental treatment. However, it is necessary to separately produce the inlays which secure the artificial tooth to the abutment teeth. It is very difficult to precisely make the prostheses due to errors caused while taking an impression and making the prostheses. The above dental prosthesis is less likely to provide the appearance or function of natural teeth.
In the case of a replacement of a missing tooth using an artificial tooth, it is necessary to form a gap between the lower portions of the natural teeth and the artificial tooth so as to allow an easy removal of impurities from between the teeth. However, the inlay of the above dental prosthesis comes into close contact with the natural tooth (abutment tooth), and so a gap is not formed between the natural tooth and the artificial tooth. This dental prosthesis causes the natural teeth to be decayed by impurities, such as food, which get stuck between the teeth. This ultimately causes severe damage to the abutment teeth and the gum.